1 files changed, 67 insertions, 0 deletions

diff --git a/src/components/ActiveSectionProvider.tsx b/src/components/ActiveSectionProvider.tsx
new file mode 100644
index 0000000..022dbad
--- /dev/null
+++ b/src/components/ActiveSectionProvider.tsx
@@ -0,0 +1,67 @@
+/*
+ * SPDX-FileCopyrightText: 2023 Kristóf Marussy
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+import { useLocation } from '@docusaurus/router';
+import {
+  type ReactNode,
+  createContext,
+  useCallback,
+  useContext,
+  useRef,
+  useState,
+} from 'react';
+
+export interface ActiveSection {
+  hash: string | undefined;
+  setHash: (hash: string | undefined) => void;
+}
+
+const ActiveSectionContext = createContext<ActiveSection | undefined>(
+  undefined,
+);
+
+export function useActiveSection(): ActiveSection {
+  const value = useContext(ActiveSectionContext);
+  if (value === undefined) {
+    throw new Error(
+      'useActiveSection is only valid inside ActiveSectionProvider',
+    );
+  }
+  return value;
+}
+
+export default function ActiveSectionProvider({
+  children,
+}: {
+  children: ReactNode;
+}) {
+  const location = useLocation();
+  const [hash, setHashState] = useState<string | undefined>();
+  const lastHashRef = useRef<string | undefined>();
+  const setHash = useCallback(
+    (hash: string | undefined) => {
+      if (hash === lastHashRef.current) {
+        return;
+      }
+      // Passing `undefined` to `hash` will give contraol pack to react-router.
+      const newURL = `${location.pathname}${location.search}${
+        hash ?? location.hash
+      }`;
+      // Update the history entry without informing react-router so Docusaurus
+      // doesn't scroll to the top of the element. See
+      // https://github.com/facebook/docusaurus/blob/ca3dba5e5eab0f8b8a9b3388e2b2e637fe3a19a7/packages/docusaurus/src/client/ClientLifecyclesDispatcher.tsx#L30-L39
+      window.history.replaceState(null, null, newURL);
+      setHashState(hash);
+      lastHashRef.current = hash;
+    },
+    [location, setHashState],
+  );
+  return (
+    <ActiveSectionContext.Provider value={{ hash, setHash }}>
+      {children}
+    </ActiveSectionContext.Provider>
+  );
+}